Cant use Tailscale's Mullvad VPN as exit node..?

Support and Troubleshooting
1

Hey guys, I bought mullvad vpn addon for tailscape, to use their exit nodes. then tried to enable it on my umbrel:

root@umbrel:/home/umbrel# ./umbrel/scripts/app compose tailscale exec web tailscale up --exit-node=100.91.198.104 --accept-routes
bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8)
bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8)
root@umbrel:/home/umbrel#

what am i doing wrong?